How To Determine Safe Piston Speed?

"Ron said they didn't worry about piston speed, as their "pistons don't fail." "

It seems strange to me that they cant ( or wont ) give you a number.

You'd think that would be basic information for a company that makes pistons.

 

Yep, you'd think!

 

Also, if they are absolutely 100% guaranteed not to fail, maybe they could be lighter...

 

When was the last time you bought guaranteed not to fail pistons to be used in a supercharged nitro burning engine? Just curious. Lippy

 

I think the three main bearing bottom end would be more of a concern than piston speed.

 

Maybe you never dealt with Venolia? They can be a pain to deal with,as in a lack of info from my several experiences buying pitons from them.

 

Reading threw this the first thing that comes to mind is

Are you making max H/P and torque at that high of RPM ? .. sounds kinda high to me for that motor.

 

I love it when someone says not to worry about something when they offer no basis for their position.

I also love it when someone offers some drag racing, or almost any racing, application as proof of why something is OK to do. You know - "Hey, Don Garlits runs 11,000RPM so there's no reason you can't!" Let's not forget most racing engines are taken apart, or come apart, far more often than the engines used by actual cars.

Piston speed? The reason you don't see too much about it is a lot of people don't understand it and therefore it must not be important.

You can bet all of the people who understand engines - for example Ford, GM, or Chrysler or Toyota or Ferrari - know plenty about piston speeds and have some very defined ideas about what's good and what's not.

Why doesn't it bother a Nissan engine to run all day long at 3500RPM? It has such a short stroke that its pistons are moving no faster than your SBC's are at 2250RPM.

I suspect Venolia is like a lot of companies - their brains retired 25 years ago and what's left are a bunch of guys doing what was done 25 years ago with no understanding of why.

 

Here's a video of 496 HP at 5000 rpm- http://www.youtube.com/watch?v=89rVb497_4c&feature=youtu.be

Here's a screen shot on the dyno at 5500 RPM.

I suspect when we go to fuel, that we'll still be making HP at 6000 RPM.

This isn't Grandma's flathead!

 

I just couldn’t imagine the exhaust side breathing at that RPM … if you say so.
Sounds like id take baby steps …. This could get ugly for the bank account.

 

The guys at Reher & Morrison Racing Engines are a good source to speak to about this subject. Email them at info@rehermorrison.com

 

Yea guys and there is a great difference in a Drag engine thats gonna be run for seconds and a bonney land speed car thats run for minutes, loads and stresses must be greater. Yea Buddy seems crazy that you could not get engineering info from the source......wierd.....

 

I've always been told that production Ford 302s blocks are iffy at 500hp and they have 5 mains.

 

4.625 is a big swing and questioning piston speed is a valid concern. You also need to consider side loading of the cylinder walls. I've found that relying on the experts is a big and costly mistake. Do your homework and research it thoroughly, it will save you big time in the end. Bearing speed, piston speeds, side load. rod to cylinder bore angle and on infinitum when calculated and adhered to during the building will make a durable power building engine.

 

Good point! You may find that stepping up to nitro you will need to put an even longer rod in it than for gas or alcohol to help reduce the greater cylinder wall loading you are going to have with using it. Also, TF and FC pistons have teflon buttons inserted into the piston skirts to help with use with nitro, do yours have them. You might need to change piston designs also for nitro, and definately if you change rod lengths.

 

In my brief time around top fuel motors about ten years ago.
I was amazed at how beefy the pistons were ... very thick all over …. I still have some around here somewhere.
Some have big dents in there tops.

 

4200 feet per second, guys are pushing it to 4500. It will start to kill the skirts over that.

 

That's the same theory as build a bridge, drive trucks of ever increasing weight over it till it breaks. Then weigh the truck, build another bridge and post a sign of the weight just before it broke.

 

Are you familiar with speedtalk.com? Lots of good tech there. You should be able to get more opinions in the engine and advanced engine tech forums.

 

I wonder how nitro is gonna like that combustion chamber? Lippy

 

Lippy, what do you mean? The shape, coating...?

 

Damn, I'm getting dizzy reading about all this piston speed and such. I am sure it is important, but wouldnt know if it even if it jumped up and bit me on the butt.

However, I cannot imagine it being even close to the importance of the correct fuel curve on any supercharged engine running nitro. Piston speed will be the last thing on your mind when it goes lean, even for a split second at rpm. Nitro under pressure (supercharged) and at rpm loves more nitro. DO NOT let it get lean on you or your piston speed will begin to slow quickly as the pistons begin to fuse to the cylinder walls or those heads. Then the fire starts and that is a real bitch at Bonneville speeds.

However, go for it man. Flatheads forever.................

JMHO

 

It would be nice if goatroper or 5xenginepro chimed in. I think someone else mentioned it in an earlier post, but I would imagine piston speed is very important at this power level since it will be run at high revs for so long.


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Our take on piston speed is: It is realitive to parts being used....and I dont know if there is a definite answer to when it implodes. There just are to many variables per engine,materials,piston weight,wrist pin flex,rod angle,ect.

Heres what I can tell you....our endurance engines have a piston speed of 5866 fpm @ 8800 and 6133 @ 9200.... 500 miles between rebuilds

Right now Im sure your Flathead is going to have many more obsticales with adding nitro and the power incresses... than piston speed.

Tony

 

Thats what Im thinking...I don't think that chamber (shape) will like much of a load.

Tony

 

I'm not a pro engine builder by any means. I was told this formula
4500 X 6 ÷ STROKE. In that case your piston speed @ 5838rpm is the same as a 3.0" stroke 301ci. Chevy at 9000rpm.

 

The problem I see is there just isn't too many people with experience pertaining to this engine ,nitro and supercharged!!! Detonation will be a top priority to stay away from. Once it starts with nitro it's just a matter of seconds before impending doom. Remember nitro carries it's own oxygen. Everything you ever learned about gasoline, throw it out the window. It does not apply. Alum rods I think are a must. For their shock absorbing qualities. This engine is uncharted territory. If it was just injected, when a lean cyl popped up it would nibble the ground strap off and like a fuse, poof cyl goes dead. No heat damage. Blown is a different story, it keeps running until you know what. Not trying to discourage you, just make you aware. We need more info here. Lippy

 

You're right- none of us knows squat about Nito, except for our dyno guy, John Beck. That's why I'm trying to learn what I can, about using small percentages of the stuff. I hope to have a good nitro tuner on board when we go to the salt, but don't have any comitments yet.

What info do you need, or would you liketo know? I'm happy to supply all info needed.

 

A guy would have to be nuts to take on the responsibility of tuning that thing!! Wait, I may know someone. I'll call him tonight gotta go back to work. Lippy

 

You're the man, Lippy!